1. Field of the Invention
The present invention relates, generally, to an aqueous cleaning solution for cleaning an integrated circuit device and a method of cleaning using the same, and more particularly, to an aqueous cleaning solution for cleaning an integrated circuit device on which a metal and polysilicon are simultaneously exposed, and a method of cleaning using the same.
2. Description of the Related Art
Generally, in a semiconductor manufacturing process, the throughput of integrated circuits is largely affected by unwanted physical and chemical contaminants. Such contaminants also affect the reliability and performance of the integrated circuits. As a design rule of an integrated circuit decreases, the cleaning and detecting of smaller size contaminants on a wafer in a semiconductor manufacturing process has become increasingly more important.
Since the development of the RCA cleaning technique in the 1960s, SC-1 (Standard Cleaning 1, NH4OH/H2O2/H2O) has been widely used for its superior particle removing capability. In a process for removing organic material, SPM (Sulfuric Peroxide Mixture, H2SO4/H2O2) has been widely used. In the SC-1 and SPM cleaning solutions, hydrogen peroxide acts as a strong oxidant. For example, by reacting with the hydrogen peroxide, an organic substance on a surface of a wafer dissolves and oxidizes. In addition, hydrogen peroxide may corrode a metal on the surface of the wafer due to the metal reacting with oxygen of the hydrogen peroxide. Further, polysilicon formed on the surface of the wafer oxides so as to form a natural silicon oxide layer. Then, the silicon oxide layer is removed together with particles on the surface of the wafer.
However, resistance of a wiring formation of the integrated circuits must be reduced as a result of the reduction of the design rule. Therefore, in order to reduce the resistance of the wiring formation, a metal, e.g., tungsten, is introduced in an early stage of forming the integrated circuit, such as a gate line fabrication stage. As a result, because the hydrogen peroxide (H2O2) component of the cleaning solutions can corrode a metal that forms a gate line, the SC-1 or SPM cleaning solution cannot be used as a cleaning solution in the process of forming the gate line. Also, the gate line is partially exposed in a subsequent process. Thus, using the SC-1 or SPM cleaning solution can corrode the gate line in the subsequent process.
To solve these problems, an aqueous cleaning solution that contains a metal corrosion inhibitor is used. A conventional aqueous cleaning solution that contains a metal corrosion inhibitor, such as aliphatic alcohol with an element of a mercapto group bound thereto, that is, 2-mercaptoethanol or thioglycerol, is disclosed in U.S. Pat. No. 6,200,947. This conventional aqueous cleaning solution is a pro-environmental cleaning solution containing a metal corrosion inhibitor and has a superior capability for removing particles, ashing residues, and/or polymers. Also, the conventional aqueous cleaning solution protects a metal such as tungsten from corrosion because it contains a metal corrosion inhibitor. However, the conventional aqueous cleaning solution has a high etching characteristic toward polysilicon. Therefore, when cleaning a wafer with exposed polysilicon using the conventional aqueous cleaning solution, undercutting of the polysilicon or Si pitting can occur.
Another conventional aqueous cleaning solution that is widely used for cleaning a metal includes a cationic surfactant or a nonionic surfactant. When the conventional aqueous cleaning solution that contains one of these surfactants is used, the cleaning ability is improved due to the superior foaming characteristics of the cleaning solution. However, such an aqueous solution generates a lot of foam during a cleaning process. As a result, excessive generation of foam can cause an overflow of the cleaning solution in a cleaning bath, which can deteriorate a uniformity of a cleaning effect on a wafer because some of the foam can adhered to the surface of the wafer. This incomplete cleaning can cause a defect on the integrated circuit substrate.
Meanwhile, another conventional aqueous cleaning solution that can be used for cleaning a wafer on which both a metal and polysilicon are exposed is disclosed in Korea Laid-Open Patent Application No. 2002-0005388. The aqueous cleaning solution contains a silicon corrosion inhibitor that prevents corrosion of polysilicon, and is represented by the following formulas 1 or 2:HO-{(EO)x-(PO)y}z—H  [Formula 1]R-[{(EO)x-(PO)y}z—H]m  [Formula 2]
where EO is an oxyethylene radical; PO is an oxypropylene radical; and R is a remainder of an alcohol or amine without a hydrogen atom of a hydroxide radical of the alcohol or amine or a remainder of amino acid without a hydrogen atom of the amino acid.
The aqueous cleaning solution containing a non-ion surfactant represented by the above formulas 1 and 2 can prevent polysilicon from being etched. Also, the above compounds have a low defoaming rate because the compounds have a high foaming characteristic. Therefore, when the aqueous cleaning solution is used for cleaning a wafer, there is a high possibility of an overflow of the aqueous cleaning solution. Moreover, the generated foam can adhere to the surface of the wafer resulting in the wafer having a non-uniform clean surface, which can further cause defects on the surface of the wafer.